Moreover, the abundance of chemical compounds and their importance in daily life hindered the chemist from investigating the question, in what does the individuality of the atoms of different elements consist.

With this in mind, for some twenty years I have set myself as my particular task the experimental investigation of the connexion between change in the structure and change in the spectra of chemical atoms.

The emitters of the spectral series are without exception single atoms, not compounds of atoms.

The question of the composition of perceptible objects is one which already occupied the mind of the ancient Greeks.

At the head of these new discoveries and insights comes the establishment of the facts that electricity is composed of discrete particles of equal size, or quanta, and that light is an electromagnetic wave motion.

Moreover, the abundance of chemical compounds and their importance in daily life hindered the chemist from investigating the question, in what does the individuality of the atoms of different elements consist.

It is more likely that more than a century will pass before we know the structure of the chemical atoms as thoroughly as we do our solar system.